Robert Hawkins was described by a judge as an "unrepentant paedophile" as he was sentenced at the High Court in Edinburgh on Friday.
The 58-year-old was convicted of the repeated rape of two women and serious sexual offences against a six-year-old girl and a boy of the same age at various addresses in Edinburgh and Dumfries between 1990 and 2004.
He was brought to justice after investigations by Police Scotland's cybercrime and public protection units.
Lord Pentland said the "calculated and sustained" sexual abuse of the children over many years had had a devastating effect on their lives.
The judge's sentencing statement, released by the Judicial Office for Scotland following the hearing, said: "I am left in no doubt that you are a devious, ruthless and dangerous sexual predator, and an unrepentant paedophile.
"Even now you have shown no remorse and have evinced no empathy for your victims or insight into the harm you have caused them.
"Whilst you have experienced certain difficulties and challenges in your life, these cannot begin to excuse the extreme gravity of your offending.
"You are an intelligent man and must have been fully aware how profoundly wrong your conduct was."
During the trial Hawkins pleaded guilty to the possession of a large number of indecent images of young children between 2006 and 2016.
His screensaver played images of children being abused, and chat logs recovered from his computer showed he communicated with other paedophiles.
Hawkins was jailed for 14 years after which he will be on licence for five years.
Detective Sergeant David Brady said: "Robert Hawkins is a dangerous and predatory individual who committed a number of extremely serious sexual offences against women and children over a prolonged period of time.
"The evidence gathered against Hawkins during our investigation was overwhelming. However, his conviction was only possible thanks to the bravery of the victims in coming forward to report the abuse that they had suffered."